One of the many complications associated with diabetes is peripheral neuropathy, which may affect up to 90% of diabetic patients with about 25% having clinical signs or symptoms. Diabetic peripheral neuropathy is defined as nerve damage attributable solely to diabetes mellitus; it can be either clinically evident or subclinical in nature and may involve the somatic and/or autoimmune nervous systems. The peripheral neuropathies are generally progressive and usually irreversible and often progress to a severe loss of sensation in the lower extremities, a condition that leads to an increased incidence of foot ulcers, infections, and amputations. The purpose of this study is to determine if CI-1014 (zenarestat), an aldose reductase inhibitor, can reverse, stabilize, or slow the progression of diabetic neuropathy relative to placebo and to assess the safety of CI-1014.